Converting a GST 7.7 to brushless. Help?
 

Hey. I'm going to convert a GST 7.7 to brushless. The car weighs approx. 17 lbs with the nitro gear. Not sure what it will weigh after the conversion is complete, but I'm guessing around 17lbs. I'm planning to run a Castle Creations 1717 @ 1580kv on 6s lipo with a Mamba Monster Max. It looks like the 1717 is the most powerful motor I can run on 6s on a MMM ESC.

But I need some help (This is my first electrical conversion.)

These are my worries;

This is a car with 2 clutch gears and 2 spurs for gears. I guess it's possible to mount a 2 speed clutch system on a 2 speed pinion adapter, like this; http://www.rc-monster.com/proddetail...adapter&cat=40

This tranny also houses the reverse, which is done by a servo via remote. How will this work with an electrical setup? I'm guessing the tranny needs to be in reverse in order to go backwards, and if I just hit reverse with the motor the tranny will pretty much go bye bye.

Also, there is no slipper clutch currently installed.

How do I solve these problems for a brushless setup? If getting a 1 speed tranny/Direct drive is the easiest solution, which should I get? Or can I just strip down the GST tranny and place the motor directly on the center diff somehow? I've seen what looks like this setup in lots of GST brushless pics. Or can I just mount the motor directly onto the spur gear like the nitro setup somehow?

Basically, what is the easiest way to get this car moving with an electrical motor? How do I get the motor mounted onto the tranny?

Whew.. lots of questions!

Thanks in advance.. :P

That 2 speed won't stand 10 seconds under a 1717 , so ditch second gear. Lock it in first and ditch reverse also. I doubt the motor and esc would work well as brakes on a truck that size so i hope you plan on mechanical braking right? For mounting the motor your best bet is probably to make a custom motor mount out of some angle or see if mike can whip you up something. I've never really seen a GST 7.7 up close so I'm just kinda spit balling here.I'm sure someone else can give you a more detailed answer.--Josh

Yep, mechanical braking. Haven't done this before, so I need to find a tutorial on mechanical brakes hen I've gotten the components (Next week I guess.).

Here's a couple of pictures of a converted GST. It looks like the guy removed the tranny and just used the center diff spur;

Attachment 9159
Attachment 9160

This is a pic of a conversion WITH the tranny;

Attachment 9157

This guy uses all the gears, and according to him it's working fine:

http://origin-images.rcuniverse.com/...97/Tq48930.jpg

The first 2 look rather well set up. The 3rd one not so much. I wouldn't listen to/ go off anyone elses design who mounts a lipo to the top of there cage,WTF?--Josh

Hehe, it looks a little weird indeed. :p

But what would be the simplest way to mount this up? Would it be to strip the tranny down to the center diff and use that, or just use the entire tranny without reverse / second and third gear? Or buy a direct drive system?

I would like to install a slipper clutch as well.

E-maxx, Revo, Savage, etc (the popular trucks) all have simple direct drop in upgrades for brushless @ RC-monster, but I'm not sure what sort of hopup would relate to this setup. I don't have the mount, motor or ESC yet, so I'm just doing some research atm. But what is the basic concept behind putting an electric motor in a nitro truck? Just put it on the tranny spur or?

I would try using the tranny locked in second (I didn't mean to say first gear sorry!) and make a motor mount out of some aluminum angle. Or email monster mike and see if he has a mount that wil work. And if you do destroy the tranny, then I'd try to find a way to use mikes universal center diff mount.--Josh

Got some pics of the GST tranny. Hopefully someone will remember a direct drive or something similar that will make this process easier:

http://i94.photobucket.com/albums/l8...n/DSC_0803.jpg

http://i94.photobucket.com/albums/l8...n/DSC_0804.jpg

http://i94.photobucket.com/albums/l8...n/DSC_0812.jpg

http://i94.photobucket.com/albums/l8...n/DSC_0816.jpg

http://i94.photobucket.com/albums/l8...n/DSC_0822.jpg

I agree, the worst that can happen is you destroy the tranny. Then use a center diff.

The pics show mechanical brakes are already set-up, so I, personally, would use them. They will save some strain on your esc with this heavy truck.

I will definitely run with Mechanical Brakes. I just need a 2.4 ghz remote with mixing capabilities then, or find another way. Not sure how to do this, but I'm taking 1 thing at a time with this. I thought I could just connect the servo together with the ESC or something in a Y harness string, and just let it go back AND forward (Like, when I hit throttle, it goes forward and does nothing, but as soon as I hit reverse, it goes backwards and brakes.)

you want a y-harness on your throttle channel: forward = forward to the esc; reverse= brakes. Just disable braking and reverse on your esc.

So, throttle servo and ESC in the Y harness to the throttle channel then?

And by the way, do you know how to grind a flat spot on the motor rotor? Or the easiest way? Thought about simply closing up the holes on the motor with lots of tape and stuff to prevent anything from entering the holes, and just do it manually. It doesn't need to be that deep.

Yes (but for you, it will be a brake servo - not a throttle servo)

Opened up the tranny today, and those metal gears look extremely solid. You guys sure these break easily?

Here's the tranny;

http://i94.photobucket.com/albums/l8...ssionsmall.jpg

From what I can understand by looking at the Revo locking guide, I have to simply remove this:

http://i94.photobucket.com/albums/l8...STGEARTHIS.jpg

And just LEAVE this be, since the centrifugal clutch is already attached to the gear, which I assume is the SECOND gear?

http://i94.photobucket.com/albums/l8...CLUTCHTHIS.jpg

Bah, been going over the gears over and over, but I can't figure out exactly how to do this. The gear that's directly on the other side of the pinions reaches down to the center diff, and if that gear was stuck to the pole I could simply remove all the others. But it isn't stuck.

The centrifugal clutch gear isn't attached to the "pole" either, and I cannot screw it or attach it to the gear next to it.

You just remove the second gear,and LOCK the centrifugal clutch in the engaged position.and then your done.I still see premature tranny destruction even being metal under a 1717,then after your tranny goes bye bye,I'd contact mike and see what he has to say or try a savage style center diff setup.--Josh